1. Field of the Invention
The invention relates generally to filters for filtering fluids, such as air. In one aspect, the invention relates to a filter assembly comprising a modular frame supporting a uniquely communicating filter medium. In another aspect, the invention relates to a filter assembly comprising a frame supporting a filter medium and a fluid quality module.
2. Description of the Related Art
Conventional forced air furnaces or central air conditioners (generically referred to as heating, ventilating, and air conditioning, or HVAC, systems) comprise a return air duct to direct air into a central unit for conditioning by either heating or cooling, and an outlet duct for distribution of the conditioned air from the central unit throughout the building. The return air duct typically has a filter disposed therein for removing dust and other particulate matter from the incoming air. As air passes through the filter, the matter is removed to prevent distribution through the home and to avoid contamination of the central unit.
Several types of filters exist for removal of matter from the air. The most common variety is a standard, rectangular panel replaceable filter, which is composed of a random arrangement of fibers, such as fiberglass, supported within an open cardboard frame. They filter the air by trapping particles within the randomly oriented fibers. Although these filters are able to capture large particles, they do little to remove smaller particles from the air. These filters primarily protect the central unit and minimize the amount of dust on the heating or cooling equipment. Their principal advantage lies in their low cost and low pressure drop.
Other filters include replaceable and reusable pleated filters, high efficiency pleated filters, high efficiency particulate air (HEPA) filters, and washable fiberglass filters. Pleated filters have a filter element that is pleated or folded to provide a large surface area for collecting particles. High efficiency pleated filters are reusable or disposable, and are also electrostatically charged to capture small particulate matter less than one micron in size. HEPA filters are efficient at removing submicron particles and comprise a core fiber that is folded back and forth over corrugated separators. The fiber is composed of very fine sub-micron glass fibers in a matrix of larger fibers. Washable fiberglass filters are similar to the conventional panel filters but can be washed and, therefore, reused.
Each type of filter has advantages and disadvantages. Pleated filters are effective at removing small particles, but they must be replaced more frequently than panel filters to avoid airflow restriction. HEPA filters efficiently remove submicron particles, but they are relatively expensive and create a higher pressure drop. Washable fiberglass filters cannot be completely cleaned to their original state and, therefore, can restrict airflow.
In many cases, the selection of an air filter must be carefully determined based upon factors such as specific health requirements of the building inhabitants, the air flow characteristics of the particular HVAC system utilized, cost, maintenance considerations, and the like. These and other factors may dictate that a specific filter, or a small selection of filters, be used exclusively, and be correctly selected and installed. Other than size differentiation, conventional filter configurations do not prevent the installation of an inappropriate filter in the HVAC system.
There are also situations where it is desirable to ensure the proper installation of the air filter or another air treatment device. For example, in Applicant's copending application Ser. No. 11/025,496, which is incorporated by reference, an air treatment device is disclosed that is sized to be inserted into a standard filter opening in a duct of a household HVAC system. One embodiment of the air treatment device is an electrostatic precipitator, which comprising an ionizing grid and a collection grid. It is preferred for best performance that the electrostatic precipitator be inserted in the duct such that the ionizing grid is upstream of the collection grid. It is desirable to have an air filter or an air treatment device who's installation is ensured.